Integrated circuits and microelectronic devices use external power supplies to provide the right amount of current and at the proper voltage to drive all of the components that may be inside the device. As the number of components inside a device increases, the amount of power needed increases as well. In addition, as the components inside become smaller, lower voltages are required. This means that the amount of current must be increased to deliver the same amount or more power.
The power delivered to the device generates heat. In order to get the highest performance, the device should have all of the power that it needs, but no extra power since the extra power is converted into unnecessary heat that slows down or may damage the device. High-speed microprocessors, for example, may require a great amount of power, and therefore current, when operating at maximum load. However, the current requirements may change in a small number of clock cycles from very low, when the processor is at idle to very high when the processor is at full load. Quickly changing the power requirements becomes more valuable as different power saving modes are used as
Integrated circuits are typically powered from one or more DC supply voltages provided by external supplies and converters, such as a high-efficiency, programmable DC-to-DC (switch-mode) power converter, for example a buck converter, located near the IC package. A buck regulator uses a DC input voltage, e.g. 48 V and provides a DC output, e.g. 2 V. A pulse-width modulation (PWM) controller, drives one or more power transistors, to switch current into filter and decoupling capacitors, and one or more large inductors or transformers. The width of the PWM signal determines the amount of voltage that is sent to the IC. The power is provided through pins, leads, lands, or bumps on the integrated circuit package. The more quickly and precisely the power can be controlled, the more power can be safely delivered, the faster the device will operate, and the less power it will consume in idle or low-power states.
The width of the pulses may be changed by modifying the leading edge of the pulse (leading edge modulation, LEM), modulating the trailing edge of the pulse (trailing edge modulation TEM), or by modifying both the leading edge and the trailing edge of the pulse (dual edge modulation DEM). In some embodiments modulating the leading edge may have a much weaker effect than an equivalent modulation of the trailing edge.